1. FIELD OF THE INVENTION
The present invention relates to rotary piston engines, and more particularly the invention relates to an ignition system for rotary piston engines. Namely, the present invention relates to improvements on such ignition system for ensuring stable combustion during the periods of low speed and load operation of the engine.
2. DESCRIPTION OF THE PRIOR ART
With a known type of rotary piston engine, a spark plug is mounted on each side of the trochoidal minor axis of the housing and the engine is operated by means of the two spark plugs. With this system, during the periods of low speed and load operation, such as, during the periods of idling operation, due to the recirculation of a large quantity of exhaust gases which is inherent to the engine itself, the combustion tends to become unstable thus giving rise to misfiring or uneven combustion with the resulting variation of the torque. While such uneven combustion can be reduced in some degree by increasing the engine speed or by decreasing the air-fuel ratio of the mixture (by enriching the mixture), this is not an effective means of overcoming the difficulty, since the increased engine speed and the enriched mixture tend to deteriorate the fuel consumption considerably. As a result, such uneven combustion results in the emission of a large quantity of HC, and moreover the increased surface/volume ratio of the working chambers results in the emission of a very large quantity of HC as compared with that of the four-cycle reciprocating engines. Thus, the rotary piston engines equipped with an exhaust gas reactor have serious problems of reactor durability and secondary air pollution due to the heating of the reactor.